Of C60 Low Creep Properties Of Concrete Research

The rail height of ballastless track after tracking can be only adjusted through fastener. However, the adjusting scope is very limited. In order to guarantee ride to be comfortable and determine appropriate track laying time, it is very significant to study the shrinkage and creep of concrete used for ballastless track bridge. Based on Ministry of Railways major project—Research for creep property of high performance prestressed concrete girder, taking the C60 high performance concrete to be used for supergiant ballastless trak bridge in Rong Gui water way as the research object, which is one of the bridges of Guangzhou-Zhuhai intercity railway traffic engineering, the influence of mineral admixture on chemical combined water of harden paste and atutogenous shrinkage of mortar as well as mechanical property, durability, shrinkage and creep of C60 high performance concrete were investigated. The main outcomes in this study are as following:1,A investigation into the influence of mineral admixture on chemical combined water of harden paste were conducted and the result shows that with the increasing incorporation of the mineral admixtures (fly ash and slag), chemical combined water of harden pastes decreases and a decreasing trend of equivalent combined water and hydration influence factor were found. The chemical combined water of harden pure cement paste is about 0.15 at 120d, which occupies 65.2% of chemical combined water needed for complete hydration of cement, this indicates that there still exists relatively many unhydrated cement particles in the harden paste.2,The result according to the experiment of autogenous shrinkage of mortar indicates that autogenous shrinkage of mortar with 0.3 water to binder ratio increases with the development of age. The 10%～20% replacement of fly ash for cement decreases autogenous shrinkage of the mortar specimen. Originally within 7 days, the 10%～20% replacement of slag for cement decreases autogenous shrinkage of the mortar specimen and increases autogenous shrinkage of the mortar specimen at later age. Compared with pure cement mortar, the 10% and 20% incorporation of fly ash into mortar reduce autogenous shrinkage of the mortar specimen by 21.1% and 29.5%, respectively. The 10%²0% replacement of slag for cement increase autogenous shrinkage of the mortar specimen by 11.1% and 6.6%, respectively.3,According to experiment of concrete mechanical properties, the suitable dosage of fly-ash and slag were determined, and influences of them on mechanical properties of concrete were investigated. The experiment test suggests that the Proportions of concrete replaced cement with 23% fly-ash and 10% slag are determined as field Proportions, and this concrete meets construction require. A formula f_pl = 0.1583f_cu^0.762 is presented for HPC compressive and splitting strength, and the index of correlation is 0.89.4,Based on experiment test of cloride ion diffusion coefficient of concrete, test shows that The 10%～30% replacement of fly ash or slag for cement can reduce chloride ion diffusion coefficient of concrete. At 28d, The chloride ion diffusion coefficient of filed concrete(23% fly-ash and 10% slag) is 4.19×10¹² m² /s, compare d with pure cement concrete, it reduces chloride ion diffusion coefficient of pure cement concrete by 35.2 %.5,By taking the concrete made with 0.5 water to binde ratio and 490 kg/m³ binder as the research object, the carbonate property of the concrete was analyzed. The carbonate depth of concrete with 23% fly-ash and 10% slag replaced cement is less, only 2.6mm. So, under the same condition of equal amount binder, carbonate is hard to carry through for concrete made with 0.29 water to binde ratio, it can be ignored.6,The experiment test of shrinkage and creep of concrete indicates creep coefficient and shrinkage deformation increase and creep rate decreases with age developping. At the same age, multiple 23% fly-ash and 10% slag can reduce the creep and shrinkage strain of concrete; concrete creep coefficient of pure cement concrete is 1.304 after loading 180d, while that of multiple concrete decreases by 10.4%, compared with pure cement concrete. After loading 180d, creep coefficient of multiple concrete with 60% handstone rate is 0.996, which reduces by 14.7% compare to multiple concrete with 58% handstone rate. During 0-180d loading time, creep coefficient with actual measurement is 0.53-0.72 times of calculated value of Chinese Railway specification and 0.5-0.73 times of calculated value of Chinese Traffic specification.The achievements of this paper can serve construction control and latter creep deformation of Rong Gui water Way Bridge, also provide references for research of other similar object.